Abstract
There have been many experimental reports concernig early ultrastructural changes of ischemic brain tissue. Common morphological changes of the early stage of the ischemic brain tissue are said to be mitochondrial swelling in the neuron and edematous enlargement of perivascular spaces. In this paper, it was reported that the actions of various agents such as Dexamethasone, Mannitol, Ergot-Alkaloids, Pentobarbital to these ischemic conditions experimentally. The ischemic conditions were obtained by ligation of both internal and right external carotid arteries of Wistar rats. The regional cerebral blood flow (rCBF) were measured in the area of the cortex and the basal ganglia of the right hemisphere.
In 73 cases of 258 experimental rats, the rCBF decreased up to 50-60% to the preoperative flow rate in 30 minutes after ligation and gradually reduced subsequently. Therefore, these animals were used for experiments.
Morphological changes of these ischemic brains were observed by electron microscope chronologically. The ischemic conditions produced mitochondrial changes in the neurons which were disintegrated with vacuolation and separation of cristae. These irreversible morphological changes of mitochondrias were increased when their ischemia were prolonged, and 3 hours after ligation, the proportion of the irreversible mitochondrias in cortical neurons attained to 54%.
Pentobarbital and Ergot-Alkaloids had significant inhibitory effect for these ischemic mitochondrial changes.
Dexamethasone and Mannitol showed no apparent protective effect for them. However, the latter two drugs reduced perivascular edema remarkably. Especially, Mannitol showed an effect to increase circulatory blood volume after recanalization by removal of the clip. Namely, the brain tissue of the group, which was administrated Mannitol during the ischemic condition, showed minimal histological changes after the blood circulation was regained, and active vesicular transports were not seen.
